Centrifugal switch for motors



NOV. 8, 1932. v C KENNEDY 1,887,261?

CENTRIFUGAL SWITCH FOR MOTORS Filed June 3, 1931 Fig.1

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The present invention switc es The 1 .i obiect of tion is to ride asimple, dnr ezpensive cent fugal switc h tive oper ion which nernvenient V9I t1011 of the opera Another object of the inve vide a centngal switch in w tating parts are required to carry curl With these andother olojects in view, will hereinafter appear, the present inve tionconsists of the centrifugal switch hereinafter described andparticularly defined in the claims.

v In the accompanying drawing, l is a sectional elevation of a motorembodying the preferred form of switch; Fig. 2 is a sec-- tion on line.%2 of Fig. 1 Fig. 3 is an elevation of the moving parts in runningposition; Fig. i is a section on line 4;'4; of Fig. 1, showing theswitch assemblies; and Fig. 5 is a view showing the switches indifferent positions.

The illustrated embodiment of the invention comprises a pressed metalframe 8 secured to the shaft 10 of the motor 12 by a set screw 13. Theframe is formed with sides 14: having outwardly extending wings 16.Between each pair of wings on opposite sides of the frame is pivoted aweight indicated generally at 18. In the'construction shown, there aretwo weights, disposed on opposite. sides of the shaft. The weights arefreely pivoted on pins connected between opposed wings.

Each weight is provided with an inwardly projecting tail portion 22 toengage a sliding collar 24. Each weight is preferably made up of aplurality of stamped laminations, all of the same shape, except that thetail portion 22 may be formed only on the central laminations. Thelaminated structure is desirable for several reasons. In the firstplace, it permits economical manufacture of the weights of any desiredmaterial, for example, of lead for low speed motors, of steel forintermediate speed motors, and of fiber or resin condensates for highspeed motors. No molding or machining operations are reattired, Furthstructure e is shown in 2, h I

laminations 25 hree steel laminations 26. The laroi ons, whatevermaterial or materials ti ay be ade, are secured gether by rivets 2? acrm the completed weight.

The outer surface of each weight is slotted, as shown at 28, to receivean arm or y Le 29.

The two arms are connected at opposite si of the frame by tensionsprings w- "'ch connected only to the ends of the arms,

ends of the springs are looped into holes 3 near the ends of the arms,An alternative set of holes 32, spaced slightly farther apart, permitscompensation for variations in the springs or weights. The two arms andthe two springs make a unitary detachable assembly, thus permitting easyreplacement with springs of varying strengths, whenever desired. Thearms normally rest in recesses 38 in the frame when the motor isstationary. In operation, when a critical speed is reached, the weightsare thrown outwardly about their pivots against the tension of thesprings. The critical speed depends on the size and composition of theweights and their distance from the axis, as well as on the strength ofthe FAG) (D springs. The desired critical speed at which the weights areto operate for any motor may be varied by alteration of any of thesefactors. Inasmuch as the centrifugal forces acting on the weights varyas the square of the speed, the weights act rapidly against the springtension when the critical speed is reached.

The collar 24 which is movable axially of the shaft, has, an annulargroove 34: within which extend the projections 22 of the weights. Thecollar is limited in its outward axial movement by a spring ring 35received in a groove in the shaft, in order that the center of gravityof each weight is always maintained inside the pivot (i. e., at the leftof the pivot, as viewed in Fig. 1) so that the Weights are alwaysrequired to swing outwardly on the tionary switch mechanisms.

1y from its initial position to a position where it engages a soft feltor rubber washer 36 secured in the frame. So long as the motor operatesat running speed, the collar, being firmly gripped by the weights andfrictional- 1y engaged by the washer, rotates with the frame, therebeing no relative movement between the collar and the weights. Thecollar bly comprises an insulating base 40 attached to the end cap ofthe motor. The base carries a fixed contact 42 and a movable contact arm44 which has a contact 46 at the end. The arm 44 is a spring armattached to a bracket 48 on the base. Suitable leads may be connectedwith the contacts. Extending from the arm 44 are a pair of smallbrackets 54 carrying a pin 56, to which a small roller 58 of insulatingmaterial is attached. The outer surface of the collar 24 is rounded, asindi-- cated at 60, to form a cam. When the motor is idle, the collarsupports the roller 58 to hold the contacts 42 and 46 in engagement, asshown in Fig. 4, but when the collar is moved axially, the roller dropsoff the cam surface,

permitting the spring contact arm to moveaway from the fixed contact, asshown in Fig. 5. The motion of the arm is transverse to the motion ofthe collar. Overthrowing or vibration ofthe contact arm upon openingmovement is prevented by a stop 62 of insulating materialfprojectingoutwardly from the base. This type of switch may be used in the usualsplit-phase motor, in which a split-phase winding is left in circuitonly at starting and is cut out of circuit as the motor approachesrunning speed.

The type of switch which acts to close a circuit upon-reaching acritical speed is in general similar to the switch described above, inthat it has a base 64 attached to the end cap, a fixed contact 66, and amovable contact 68, the latter mounted on a spring arm 70, which has aroller 7 2 acting as a cam follower. The contacts are reversed, withrespect to the contacts of the otherswitch. Idle or open position isshown in Fig. 4 and running or closed position in Fig. 5. This type ofswitch is useful in some forms of conthe motor may employ one or moreswitches of either or both types, depending on the.

colrtstruction and operation of the motor itse It will be seen that thepresent'invention comprises a centrifugal switch assembly in which norotating part is required to carry current, the rotating and slidingparts serving only to actuate the stationary switches. This not onlyresults in sudden and positive making or breaking of the circuit, butalso permits convenient replacement of the contacts without dismantlingany of the moving parts. The construction is also particulan 1yadvantageous in that it is adapted for a wide range of critical speeds.A simple change of springs only may be used for induction motors ofseveral operating speeds, while a change of springs, collars, andweights, without a change in size, covers the full range of speedsordinarily met with in stock motors. For very low speed motors, it maybe desirable to increase the size of the frame, to pivot the weights ata greater distance from the axis, a change which can be made without thenecessity of altering the size or shape of the weights.

Since the switch contacts are operated laterally of the collar, they arein no way affected by the end play of the rotor, and no specialprecautions with regard to accuracy of assembly are necessary, as is thecase with some. types of longitudinally operable contacts. Moreover, theswitches do not produce any end thrust, and do not interfere with the"movement of the collar; in fact, at starting, the final movement of thecollar is facilitated at the instant of operation of the switches by thepressure of the switch rollers against the curved outer cam edge of thecollar, thus contributing to the quick opening or closing of thecontacts when the critical speed is reached,

Durability and quiet operation are assured because there is no relativemovement between any parts when the motor is running. At starting orstopping, the collar is held against rotation by the switch rollers, sothat the wear on the rollers is very slight, al

though some relative rotation between the weights and the collar occurs.However the period during which relative movement ma occur between anyof the parts is small, an after the motor comes up to speed, therotating parts all move as a slngle unit, without any connectionwhatever with the switch members. I Having thus described the invention,What IS claimed 1s: a

1. A centrifugal switch mechanism for a motor having, in combination, arotatable frame, and weights carried by the frame, each comprising aplurality oflaminations of dissimilar materials including some lamina--tions of-wear resisting material.

2. A centrifugal switchmechanism for a motor having, in combination, arotatable means a frame, opposed weights carried by the frame movableoutwardly upon rotation of the frame, the weights having notches,detach-' able arms received in notches of the separate weights, andsprings connecting the arms.

3, A centrifugal switch mechanism for a motor having, in combination,a,rotatable frame, weights carried by the frame and movable outwardlyupon rotation of the frame, a collar engaged by the weights and movableaxially, a stationary switch having a movable contact supported by thecollar when the frame is stationary, and means for resisting rotation ofthecollar during starting and stopping and permitting rotation thereofwith the frame under running conditions. T

a. A. centrifugal switch mechanism for a motor having, in combination, arotatable frame, weights carried by the frame and movable outwardly uponrotation of the frame, an axially movable cam engaged by the weights, astationary switch having a fixed contact, and a laterally movablecontact sup-- ported by the cam when the frame is stationary anddisengaged from theficam upon movement thereof.

5. A centrifugal switch mechanism for a motor having, in combination, arotatable frame, weights carried by the frame and movable outwardly uponrotation of the frame, an axially movable cam engaged by the weights, astationary switch having a fixed contact and a laterally movablecontact, the laterally movable contact being supported out of engagementwith the fixed contact by the cam when the frame is stationary, andmovable into engagement with the fixed contact upon axial movement ofthe cam.

- 6, A centrifugal switch mechanism for a motor having, in combination,a rotatable frame, weights carried by the frame and movable outwardlyupon rotation of the frame, an axially movable cam engaged by weights, astationary switch having a fixed contact and a laterally movablecontact,

' the laterally movable contact being supported in engagement with thefixed contact by the cam when the frame is stationary, and movable ontof engagement with the fixed contact upon axial movement of the cam.

l. iicentrifugal switch mechanism for a 7 motor having, in combination,a rotatable e, weight-s earned by the frame and movable outwardly uponrotation of the n axially movable cam engaged by as, a. stationaryswitch having a ct and a laterally movable contact, or ly movablecontact being supporte gaeernent with the fixed contact by out ofengagement with the fixed J upon axial movement of the cam, and rlimiting the travel of the movable 8, A centrifugal switch mechanism fora motor having, in combination, a rotatable frame, weights carried bythe frame and movable outwardly npon rotation of the frame, an axiallymovable cam engaged by the weights, a stationary switch having a fixedcontact and a laterally movable contact, and a roller carried by themovable contact and engaged by the cam when the frame is stationary andadapted to be disengaged vfrom the cam when the frame is rotatin 9. Acentrifugal switch mechanism or a motor, having, in combination, arotatable frame, weights carried by the frame, a member movable axiallyby the weights, switch contacts, and means for operating the com tactsby the axially movable member, the switch contacts acting at the instantof op eration thereof to press the axially= movable member in thedirection of its movement.

10. A centrifugal switch mechanism for a motor having, in combination, arotatable frame, weights carried by the frame, a mom her movable axiallyby the weights, and a the frame is stationery, the axially movabldmember having a curved cam surface to permit lateral movement of thecontact and to facilitate axial movement of the member out of engagementwith the contact.

12. A centrifugal switch mechanism for a motor having, in combination, arotatable "frame, weights carried by the frame, a collar 'movableaxially by the Wei hts and having a cam surface, and a plum ity ofstationary switches, each having a movable contact supported by thecollar in inactive position and laterally movable upon axial movement ofthe collar,

In testimony whereof I have signed my name to this s ecification.

- (PARLTON L. KENNEDY.

when the frame. is stationary, and

